The present invention relates generally to a ring fan shroud assembly and more particularly, to a ring fan shroud assembly with dynamic sealing properties.
Axial flow fans move air, or other fluids, using rotating impeller blades. As the impeller blades rotate, different pressures on opposing sides of the blades are developed. The discharge side of the impeller blades typically develops a high pressure while the intake side develops a low pressure. The pressure differential between these two sides can cause the fluid to flow from the high-pressure discharge side to the low-pressure intake side near the tips of the impeller blades. It is well known that this back flow can decrease the efficiency of the fan and may lead to undesirable noise generation.
One approach to reducing or preventing the back flow of air has been to minimize the gap between the blade tips and a surrounding shroud (commonly known as xe2x80x9ctip gapxe2x80x9d). This often involves tight tolerances in fan assembly manufacturing and design. Although backflow may indeed be reduced through minimization of the tip gap, the required tight tolerances can give rise to a host of complications. The tight tolerances commonly involve costly manufacturing and design to ensure that the impeller blades do not contact the surrounding shroud. Manufacturing, shipping, installation and operation all can be negatively impacted in attempts to minimize tip gap while still providing adequate clearance. Due to these complications, there are practical limitations which limit the minimization of tip gap, and therefore back flow often remains present.
Another approach to dealing with the back flow issue has been to form the shroud to provide a unique path for the back flow to recirculate through the impeller blades. These systems, instead of attempting to eliminate the back flow, reduce the impact of the back flow on the efficiency and noise characteristics of the fan. Although these configurations have been proven to reduce the impact of the back flow, effects can still be discernable. Methods and configurations attempting to minimize the impact of back flow, are often limited by the existence and quantity of back flow present. Therefore, reductions in quantity, or elimination of back flow, may prove to be more beneficial than attempts to minimize back flow impact.
It would therefore be highly desirable to have a fan and shroud assembly that was effective in reducing the quantity of back flow over the impeller blade tips. It would further be highly desirable to have such a fan shroud assembly that was not subject to the complications associated with designs attempting to minimize the clearance between the impeller blade tips and the shroud.
It is therefore an object of the present invention to provide a fan and shroud assembly with reduced back flow. It is a further object of the present invention to provide a fan and shroud assembly with an improved efficiency and reduced noise generation.
In accordance with the objects of the present invention, a fan assembly is provided. The fan assembly includes a plurality of impeller blades positioned within a rotating ring element. The rotating ring element includes a flared inner discharge surface. The fan assembly further includes a shroud element having an exit flange surface. The exit flange surface is substantially coincidental with the flared inner discharge surface.
Other features, benefits and advantages of the present invention will become apparent from the following description of the invention, when viewed in accordance with the attached drawings and appended claims.